glGetTexGen returns in params
selected parameters of a texture coordinate generation function that was
specified using glTexGen. coord names one of the (s, t, r, q) texture coordinates,
using the symbolic constant GL_S, GL_T, GL_R, or GL_Q.

params returns the four plane equation coefficients that specify eye linear-coordinate
generation. Integer values, when requested, are mapped directly from the
internal floating-point representation. The returned values are those maintained
in eye coordinates. They are not equal to the values specified using glTexGen,
unless the modelview matrix was identity when glTexGen was called.